The object of the proposed investigation is to gain additional insight into the molecular events and regulatory implications in messenger-RNA metabolism in cultured mammalian cells. Human (HeLa S3) cells infected by and rat embryo cells transformed by adenovirus will be employed in these investigations. In the lytic infection the following aspects of viral RNA metabolism will be explored. Transcription of the genome will be examined by electron microscopy following dispersal of nuclear contents. Processing of apparent large molecular weight nuclear-precursor RNA will be examined by analysis of 5'-termini and by analysis of RNA synthesized in the presence of adenosine analogues. Fate by cytoplasmic viral RNA will be determined in enucleated cells (cytoplasts). Much of the proposed study will depend upon limited RNA structure analysis, especially if viral RNA sequences which remain in the nucleus can be isolated. In addition, information bearing on the mechanism of formation of virions and restriction of host-cell RNA synthesis should also be elucidated. The feasibility of extending these investigations to adeno 2-transformed rat embryo cells, which will depend on the incorporation of sufficient radioactivity, will be constantly evaluated. These investigations should not only bear on the cell biological implications of the biogenesis of messenger-RNA but also on the infection and transformation of cultured mammalian cells.